DE69815882T2 - PLANT OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

TECHNICAL PART

The present invention relates to a system of an internal combustion engine according to the preamble of the claim 1. The invention particularly relates to harmful emissions of a diesel engine that is equipped with a system, which is the repatriation of Exhaust gases in the engine intake, a so-called EGR system ("Exhaust gas recirculation" or "exhaust gas recirculation"). The invention also relates to a method according to the preamble of claim 9.

BACKGROUND OF THE INVENTION

In connection with trucks powered by a diesel engine, there is a general need to reduce, as far as possible, the emission of harmful contaminants from the engine exhaust. These emissions are primarily nitrogen oxide compounds (NO _x ), carbon monoxide (CO) and hydrocarbons (HC). Various measures can be taken to reduce these emissions. For example, it is already known that the construction of the combustion chamber in the cylinder of the engine and the injection process of the fuel can be carried out in such a way that the emissions are minimized. In cases where the engine is equipped with a turbocharger, the NO _x compounds can be reduced by cooling the intake air of the engine (known as "intercooling" or "charge air cooling").

In connection with gasoline engines, the exhaust gases are usually cleaned using a catalytic converter installed in the exhaust system. Since a diesel engine is operated with an excess of air, the three-way catalytic converter cannot be used to reduce NO _x compounds from a diesel engine.

Due to the increasing environmental requirements and expected future statutory requirements, the need to reduce emissions, become increasingly primarily of NO _x compounds from diesel engines. In this context, it is already known that the amount of NO _x compounds from a diesel engine can be reduced by equipping them with a so-called EGR system (exhaust gas recirculation or exhaust gas recirculation), with which a certain amount of exhaust gases from the engine outlet is returned to its inlet. The amount of NO _x compounds produced in a diesel engine is in principle proportional to the temperature inside the combustion chamber, and when using an EGR system, the local temperature during combustion can be reduced by dilution with exhaust gases (CO ₂ and H ₂ O). This then leads to a lower formation of NO _x .

A diesel engine can use an EGR system equipped by using a separate connecting line between the conventional Exhaust gas outlet of the engine and a place close to the fresh air intake of the engine is manufactured. In this line there is a controllable one Valve arranged, this valve further to a control unit connected. Dependent on from the existing operating conditions of the engine, especially in terms of its speed and load, the control unit will open the angle of the valve, that is: the amount of EGR gases that are returned to the intake of the engine. A certain amount of EGR gases is released from the engine exhaust fed to its inlet by the outlet pressure, which is generally higher than that Inlet pressure is what a natural "pressure drive" or a pressure drop to Drive for the EGR gases is created.

In cases where a diesel engine equipped with an EGR system and is operated together with a turbocharger device, A problem arises from the fact that for most of the operating points behind the compressor of the turbocharger (that is: at the location of the intake manifold or intake manifold of the engine where the incoming Fresh air is supplied to the engine) a higher one There is pressure than in the exhaust gas outlet of the engine. This means then again that a repatriation of the EGR gases may not be possible is because no natural Pressure drive or pressure drop from the engine outlet to his admission. This way, no EGR gas flow in be blown into the engine.

In accordance with the known Technology can solve this problem by using the turbocharger is equipped with a variable turbine geometry. A device the this solution is described in JP-08270454 A, wherein a diesel engine with a turbocharger is disclosed, which then again has adjustable guide vanes which are dependent from the operating states the motor can be adjusted to a specific position by means of a control unit can. This way, a sufficiently high one Pressure is created in the engine outlet, creating a required Amount of EGR gases can be returned to the inlet.

A major disadvantage of this known device refers to the fact that there is a deteriorated gas exchange in the engine. consequently makes this devices for the engine required, which is in a turbocharged diesel engine a current of EGR gases without deteriorating gas exchange.

SUMMARY OF THE INVENTION

The aim of the present invention is to provide an improved system for an internal combustion engine, in particular a diesel engine, which is equipped with an EGR system and a turbocharger, this device providing a sufficiently high pressure drive or pressure gradient for the EGR gases, in order to achieve such a to obtain reduction of NO _X emissions of the engine. This goal is achieved by a plant, the properties of which are defined in the appended claim 1. This aim is also achieved by a method, the properties of which are defined in the appended claim 9.

The system according to the invention is intended for an internal combustion engine, which comprises: at least one cylinder, an inlet for the supply of air, an exhaust gas outlet for the outflow of exhaust gases, a further line for the return of exhaust gases from the outlet into the inlet for the reduction of harmful emissions the machine (in the form of CO, NO _X and HC compounds), a controllable valve arranged in this further line and a turbocharger unit which comprises a first means for absorbing energy from the exhaust gases and a means for compressing air to the inlet. The invention is characterized in that it contains a second means for absorbing energy from the exhaust gases, which is arranged downstream of the first means in order to build up a pressure in the outlet which exceeds the pressure in the inlet.

According to a preferred embodiment of the Invention the machine with an EGR system and a system be equipped for further energy absorption from the exhaust gases, which this energy of this machine returns to the crankshaft of the machine. On this way it is guaranteed that the required pressure drive or pressure drop the exhaust side is built up without sacrificing performance the machine is because the deteriorated gas exchange due to further energy consumption from the exhaust gases and the recirculation the crankshaft is compensated.

Preferred configurations of the invention are in the accompanying subclaims described.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below Regarding a preferred embodiment and on the attached Drawing described in more detail, which an inventive system represent in schematic form.

PREFERRED EMBODIMENT

1 shows a schematic representation of a system according to the present invention, which can be used especially for an internal combustion engine in the execution of a diesel engine. According to a preferred embodiment, the diesel engine 1 intended for use in a truck and includes six cylinders 2 , However, the invention is not limited to a specific number of cylinders or a specific cylinder configuration.

The motor is in a known manner 1 with an inlet manifold 3 or intake manifold, which air from the atmosphere through an inlet pipe 4 is fed. The intake air or intake air is then applied to the various cylinders 2 divided up. Furthermore, the cylinders 2 by a corresponding number of fuel injection units 5 each of which is connected to a central control unit 6 Fuel is connected via an electrical connection 7. The control unit 6 is preferably computer-aided and is used in a known manner to control the fuel injection units 5 so that at all times the engine 1 is supplied with a suitable fuel / air mixture.

While the engine is running 1 the control unit serves the respective fuel injection units 5 to control the fuel / air mixture with which the engine 1 is supplied, is adapted to the prevailing operating conditions at any time. The fuel supply is hereby obtained in a generally known manner, that is to say: as a function of a large number of parameters which determine the operating states of the engine in question 1 and represent the vehicle. For example, the control can be carried out as a function of the current throttle valve position, the speed and the load on the engine.

Every cylinder 2 is with an exhaust outlet 8th Mistake. The exhaust outlets open together 8th into an exhaust manifold 9 or exhaust manifold, which is then in an exhaust pipe 10 continues. This exhaust pipe runs over a turbocharger unit 11 , which as such is essentially conventional. So includes the turbocharger unit 11 a means of absorbing energy from the exhaust gases in the form of a turbine 12 which in the exhaust pipe 10 is arranged and of the exhaust gas flow through the exhaust pipe 10 is rotated through. As an alternative to the embodiment shown in the drawing, which is designed so that the exhaust outlets 8th in a single exhaust pipe 10 open (known as "single inlet"), the exhaust gas outlets can be arranged in two groups, whereby the exhaust pipe then consists of two pipes that go into the turbine 12 lead (known as "twin entry").

The turbine 12 is on a wave 13 arranged on which a compressor 14 is arranged in the same way. The through the turbine 12 The energy absorbed from the exhaust gas flow is transferred to the compressor 14 transmitted, which serves to suck the air into the inlet pipe 4 of the motor 1 to condense. In this way, an increased amount of fuel can the engine 1 can be supplied, whereby its performance can be increased.

The motor 1 is also with a device for returning a certain amount of exhaust gases into the intake side of the engine 1 equipped. According to what was discussed in the introduction, an EGR system ("Exhaust Gas Recirculation" or exhaust gas recirculation) is already known as such. According to the embodiment, therefore, another line is in the form of an EGR line 15 to the exhaust pipe 9 connected, at a point in the direction of flow in front of the turbine 12 , The EGR leadership 15 kinks in the inlet pipe 4 at a point in the direction of flow in front of the inlet manifold 3 of the motor 1 , Along the EGR line 15 is an adjustable valve 16 arranged, which on the control unit 6 via another connection 17 connected. The control unit serves in accordance with what has now been described in more detail below 6 the valve depending on the current operating status 16 to be moved to a closed, open or partially open position. Depending on the position of the valve 16 is a corresponding amount of exhaust gas in the intake manifold 3 can be returned via the EGR line. By returning these EGR gases to the inlet manifold 3 is in the respective cylinder during combustion 2 a reduction of the temperature attained, wherein the NO _x generation in the cylinder 2 is reduced.

The NO _x generation in the respective cylinder 2 is temperature dependent and it is therefore desirable to measure the temperature of the gases (ie: including air and EGR gases recirculated) in the engine 1 come down as far as possible. For this purpose the EGR management is 15 with a cooler 18 provided, the function of which is that in the inlet manifold 3 to cool returned EGR gases. For this purpose, the cooler includes 18 a coiled tubing 19 through which a suitable coolant flows. This coolant is preferably the conventional coolant for the engine 1 , but air can also be used for this cooling. By means of this cooler 18 the EGR gases can be cooled, which further helps to reduce the amount of NO _x compounds produced.

The inlet pipe 4 is with another cooler 20 (known as "Intercooler" or "intercooler") equipped to cool the by the compressor 14 supplied compressed air is used. This also contributes to reducing the generated amount of NO _X compounds in which in the motor 1 be generated. The second cooler 20 is preferably provided for air cooling, which is shown schematically by the reference symbol 21 is indicated.

According to the invention, a second turbine 22 used to absorb energy from the exhaust gases. The engine 1 leaving and through the first turbine 12 Exhaust gases flowing through are thus also through the second turbine 22 passed, which is thereby rotated. For this purpose the second turbine 22 rotatable on another shaft 23 arranged. After the exhaust gases transfer some of their energy to the second turbine 22 transmitted, they are discharged into the atmosphere, preferably via a silencer (not shown).

In addition, the second turbine 22 with the output crankshaft 24 of the motor 1 via a power transmission 25 connected, which is not shown in all details and is indicated in the drawing with a dashed line. The power transmission 25 is preferably of mechanical design with a gear, which the shaft 23 with the crankshaft 24 combines. The power transmission is also with a gear reduction to implement the speed of the second turbine 22 to a suitable speed for the crankshaft 24 Mistake. In this way there is power between the second turbine 22 and the crankshaft 24 transferred, that is, a certain amount of energy in the combustion gases is recovered from the exhaust gas flow and as additional power for the crankshaft 24 can be used.

A system for an engine with a turbocharger unit, which is designed to take up a certain amount of energy from the exhaust gases and conducts this energy back to the crankshaft of the engine, is usually referred to as a "turbo compound" system. By using the two turbines according to the invention 12 . 22 , which are arranged one behind the other, when the engine is operating 1 on the exhaust side of the engine 1 reached a pressure higher than the pressure on its inlet side. This is sufficient pressure drive or pressure drop for the return of EGR gases in the inlet manifold 3 acquired without sacrificing the performance of the engine 1 is affected. A part of the energy contained in the exhaust gases is used here as an additional power to the crankshaft 24 to transmit instead of dissipating this energy into the atmosphere and thus losing it.

According to what has been described above, the invention includes a controllable valve 16 in connection with the control unit 6 , Depending on the current operating status of the engine 1 and the vehicle in general, the valve 16 used in such a way that a certain amount of exhaust gases from the respective outlets 8th of the motor 1 back to the Inlet manifold are directed. According to a preferred embodiment, the valve exists 16 from an electronically controlled valve, which is operated by the control unit 6 can be continuously adjusted between an open and a closed state. By a specific setting of the opening area of the valve 16 in the EGR line 15 becomes a corresponding flow quantity of EGR gases into the inlet manifold 3 reached.

To control the valve 16 is the control unit 6 designed to determine the speed and load (torque) of the engine and, depending on these parameters, to calculate the desired amount of EGR gases to be returned to the intake manifold. This amount of EGR gases is preferably in the control unit 6 based on a stored table, which indicates the required amount of EGR gases as a function of speed and load. The valve becomes dependent on the calculated value of the amount of EGR gases 16 in an associated position via a signal from the control unit 6 brought.

In connection with the recirculation of EGR gases the returned quantity adjusted with respect to predetermined limits for soot and carbon monoxide which are released with the exhaust gases. Because the EGR feedback the amount of available Air reduced in the intake of the engine, must be determined that the air volume is sufficient in relation to the specified limit values is.

Using the valve described above 16 , which can be steplessly brought into a desired position, will result in a very large variation in the opening area of the valve 16 between different extremes of the operating conditions of the engine 1 reached. This variation is required for the plant according to the embodiment, with energy from the second turbine 22 on the crankshaft 24 is transmitted because the pressure difference between the exhaust side and the intake side varies to a large extent as a function of engine load. As a comparison, it can be stated that this pressure difference varies considerably more than in previously known systems which have turbocharger units with variable turbine geometry. By means of the control of the valve according to the invention 16 A correct flow of EGR gases can be determined, which is essentially independent of the operating state of the engine 1 is.

In addition to controlling the valve 16 as a function of the speed and the load or the torque of the engine 1 can the control unit 6 also have a function, the valve 16 to control depending on other parameters. For example, transients can be considered to cause unwanted popping and smoke in the engine exhaust 1 to avoid.

In addition, the control unit 6 also a function to enable the control of the injection times of the respective fuel injection units 5, essentially independent of the prevailing speed and load. For the control of the valve 16 it is the main thing that the flow of the EGR gas is adjusted for an optimal reduction of NO _X emissions. Then the injection timing is set for a minimum of fuel consumption, but without exceeding the given NO _x level. It is used here that the injection point in time is set as early as possible, since this is the engine's fuel consumption in a known manner 1 reduced. It is also used that the greater the flow of EGR gases, the earlier the possible injection time for a given NO _x level.

In the preferred embodiment, each cylinder 2 of the motor 1 Equipped with two intake valves (not shown) through which air and EGR gases are drawn in. The reason is that the motor according to the invention 1 an air / fuel mixture as large as that of an engine without EGR recirculation is required for good combustion without large amounts of smoke in the exhaust gas of the engine 1 to get. This in turn means that a larger gas flow (i.e. the fresh intake air together with the EGR gases) into the engine 1 must be sucked. So as not to deteriorate the flow properties and the pressure drop across the motor 1 According to the invention, it is an advantage to enlarge the motor 1 with two intake valves per cylinder 2 to provide, that is, two relatively small intake valves instead of a relatively large intake valve. It is also an advantage from a convincing point of view to use two smaller valves instead of one large valve.

The invention is not limited to the exemplary embodiment described above, it can vary within the scope of the appended claims. For example, the valve 16 be designed as an ON / OFF type, ie it can only be adjusted to an open or closed state.

As an alternative to the electronically controlled valve described above 16 the valve can be designed as a pneumatically controlled valve. In such a case, the control unit 6 be designed to operate an electromagnetic valve (not shown) (known as a PWM valve) to allow air from a compressed air source (not shown) to flow through when activated. Using this compressed air, the valve can be activated to assume a desired position.

Instead of using a single controllable EGR valve 16 Two or more such controllable valves can be used according to an alternative embodiment. To the For example, the exhaust outlets 8th be divided into two groups of three outlets each, with two pipes leading to the turbine 12 lead instead of a construction of the exhaust gas outlets 8th to flow into a single exhaust pipe 10 (compare drawing). If two such groups are used, exhaust gases flow through each of these groups (each from three cylinders) to an exhaust pipe which is provided with an EGR valve. The control unit also serves 6 to control the two EGR valves independently of each other. To expand the function in this case, the two EGR valves include valves with an ON / OFF control, which can consist of a relatively small EGR valve and a relatively large EGR valve. In this way, three different states are determined, which depend on whether each valve is open or closed. Depending on which valve is activated by the control unit, there are three different orders of magnitude of EGR gases supplied by the engine.

Claims (10)

Installation of an internal combustion engine ( 1 ) containing at least one cylinder ( 2 ), an inlet ( 3 . 4 ) for the supply of air, an exhaust outlet ( 9 . 10 ) for the discharge of exhaust gases, another line ( 15 ) for the return of exhaust gases from the outlet ( 9 . 10 ) in the inlet ( 3 . 4 ) to reduce harmful machine emissions ( 1 ), one in this further line ( 15 ) arranged controllable valve ( 16 ) and a turbocharger unit ( 11 ), which is a first means ( 12 ) for energy absorption from the exhaust gases and a means ( 14 ) to compress air to the inlet ( 3 . 4 ), characterized in that it comprises a second agent ( 22 ) for absorbing energy from the exhaust gases, which in the direction of flow behind the first means ( 12 ) is arranged to a pressure in the outlet ( 9 . 10 ) which build up the pressure in the inlet ( 3 . 4 ) and a power transmission ( 25 ) between the second means ( 22 ) and a crankshaft that works with the machine ( 1 ) is connected. System according to claim 1, characterized in that the machine ( 1 ) is a diesel engine. System according to one of the preceding claims, characterized in that the further line ( 15 ) with a cooler ( 18 ) is provided to the in the inlet ( 3 . 4 ) to cool returned exhaust gases. Installation according to one of the preceding claims, characterized in that the first means ( 12 ) and the second means ( 22 ) for energy absorption from the exhaust gases in the outlet ( 9 . 10 ) consist of turbines that are driven by the exhaust gases. Installation according to one of the preceding claims, characterized in that the valve ( 16 ) consists of an electronically controlled valve, which can be continuously controlled between an open and a closed position. System according to one of claims 1 to 4, characterized in that that it contains at least two controllable valves, each of which has an open one and can assume a closed state, each independently of the other can be regulated, whereby different opening states in stages can be obtained. System according to one of the preceding claims, characterized in that the further line ( 15 ) with the outlet ( 9 . 10 ) at a point in the direction of flow before the first mean ( 12 ) is connected to the absorption of energy from the exhaust gases. System according to one of the preceding claims, characterized in that the cylinder ( 2 ) includes two intake valves for the supply of intake air. Process for reducing harmful emissions from an internal combustion engine ( 1 ), which includes: energy consumption by means of a turbocharger unit ( 15 ) from the exhaust gases coming from the machine ( 1 ) Compression of the intake air of the machine ( 1 ), through a valve ( 16 ) regulated return of the exhaust gases of the machine ( 1 ), which in one line ( 15 ) which has an outlet ( 9 . 10 ) the machine ( 1 ) with an inlet ( 3 . 4 ) the machine ( 1 ) connects, characterized in that there is further energy consumption from the exhaust gases in the flow direction behind the turbocharger unit ( 11 ), where in the outlet ( 9 . 10 ) a pressure is built up which corresponds to the pressure in the inlet ( 3 . 4 ), and transfer of power from the agent ( 22 ) the further energy consumption from the exhaust gases in the flow direction behind the turbocharger unit to a crankshaft ( 24 ) with the machine ( 1 ) related. A method according to claim 9, characterized in that there is a cooling of the returned exhaust gases includes.